I have used both WriteRight and the BoxWave anti-glare, and I'd say go with the Boxwaves. They last for at least half a year/one year unless you really abuse them with keys in your pocket and things like that. The Writerights are usable but not as clear as the Boxwaves and also feel a bit rubbery, so not as nice with a stylus. The wiki has some tips to apply them without dust/bubbles.

B.t.w. I have also used Vikuiti by 3M and they look and feel much like the Boxwaves, but the seem to be sold mostly in Europe.